不是不 / 没有…不 / 不能不【búshì bù / méiyǒu … bù / bùnéng bù】

Two negatives in one sentence cancel out and leave a positive with something extra: a softened answer, "every single one", or "have to".

不是不: "it's not that…"

不是不 denies a negative someone might assume, usually before giving the real reason. The positive it leaves is weak, and a 只是 or 是 clause often follows.

With a past event, the second negative is 没: 我不是没告诉你 "it's not that I didn't tell you".

没有…不: "every single one"

没有 + noun + 不 + verb says there is no one, or nothing, that doesn't do it. It is stronger than 都.

不能不: "can't not, have to"

不能不 + verb says there is no choice. 不得不 means the same and is more common in writing.

The second negative

After a modal like 能 or 会 the second negative is always 不, even for a past event. And the noun in 没有…不 goes between the two negatives.

• × 我不能没去 → 我不能不去
• × 没有不人喜欢他 → 没有人不喜欢他